1. Field of the Invention
This invention generally relates to a metallic implant for biomedical use. In particular, the present invention relates to medical implants with enhanced capability for tissue-to-implant and bone cement-to-implant integration.
2. Description of the Background
Restoration of skeletal defects or wounds such as femoral neck fracture and spine fusion is a common procedure. For example, over 500,000 and 250,000 procedures are performed annually in the U.S. for hip prosthesis implantation and spine fusion surgery, respectively. Meanwhile, about 74 million people in the U.S., which amounts to about 30% of adult population in the U.S., have at least one qradrant of posterior missing tooth that needs to be restored.
Some metallic materials such as titanium are proven biocompatible materials. For example, use of titanium implants has become a standard treatment to replace missing teeth and to fix diseased, fractured or transplanted bone. Restorative treatment of missing teeth using dental implants such as titanium implants have considerable oral health impact, by which masticatory function (Carlsson G E, Lindquist L W, Int. J. Prosthodont 7(5):448-53 (1994); Geertman M E, et al., Community Dent Oral Epidemiol 24(1):79-84 (1996); Pera P, et al., J Oral Rehabil 25(6):462-7 (1998); van Kampen F M, et al., J Dent Res 83(9):708-11 (2004)), Speech (Heydecke G, et al., J Dent Res 83(3):236-40 (2004)) and daily performance and quality of life (Melas F, et al., Int J Oral Maxillofac Implants 16(5):700-12 (2001)) are improved, when compared to the conventional removable denture treatment. In treatments of facial defect resulting from cancer or injury, the use of endosseous implants is crucial to retain the prosthesis (Roumanas E D, et al., Int J Prosthodont 15(4):325-32 (2002)). However, the application of implant therapy in these fields is still limited because of various risk factors including anatomy and quality of host bone (van Steenberghe D, et al., Clin Oral Implants Res 13(6):617-22 (2002)), systemic conditions including diabetes (Nevins M L, Int J Oral Maxillofac Implants 13(5):620-9 (1998); Takeshita F, et al., J Periodontol 69(3):314-20 (1998) and osteoporosis (Ozawa S, et al., Bone 30(1):13743 (2002)), and ageing (Takeshita F, et al., J Biomed Mater Res 34(1):1-8 (1997)). More importantly, long healing time (about 4-10 months) required for titanium implants to integrate with surrounding bone restricts the application of this beneficial treatment. For example, in the U.S., dental implant therapy has penetrated into only 2% of the potential patients.
In the orthopedic field, the restoration of femoral neck fracture or spine fusion, for example, is a common problem. For example, of over 250,000 procedures performed annually in the U.S. for spine fusion surgery, about 30% or more of patients fail to achieve a solid bony union. The nature and location of bone fracture at these areas do not allow for bone immobilization (e.g., cast splinting) for better healing.
Therefore, there is a need for faster and stronger fixation of bone by metallic implants. There is also a need for stronger bone cement-metallic implant interfacial strength. The embodiments described below address the above identified issues and needs.